1. Field of the Invention
The present invention relates to novel platinum/olefin complexes, and, more especially, to platinum/triene complexes useful as hydrosilylation catalysts, to the preparation thereof and to organopolysiloxane compositions comprising such catalytic complexes.
2. Description of the Prior Art
Many compounds and complexes of platinum have to date been proposed to this art to promote the addition reaction of an organohydropolysiloxane having .tbd.SiH groups to a diorganopolysiloxane containing hydrocarbon radicals which are alkylenically unsaturated, for the purpose of forming an addition product comprising an added silicon-carbon bond.
This addition reaction can be represented schematically in the following manner: ##STR2##
One of the first such catalysts was chloroplatinic acid, as described in U.S. Pat. No. 2,823,218, or platinum metal arranged on a finely divided support, as described in U.S. Pat. No. 2,970,150.
In U.S. Pat. Nos. 3,159,601 and 3,159,602, platinum/olefin complexes were proposed for the purpose of reducing the disadvantages inherent in the use of finely divided platinum or chloroplatinic acid, the disadvantages being related to poisoning of the catalyst and to its excessively low reactivity. With the same object, in U.S. Pat. No. 3,220,972, the reaction products of platinum derivatives with alcohols, aldehydes and ethers were proposed as a catalyst.
More recently, in U.S. Pat. Nos. 3,715,334, 3,775,432 and 3,814,730, there were proposed complexes of platinum and vinylsiloxane, treated with a base, in which complexes the ratio of halogen to platinum is between 0, or a decimal number close to 0, and approximately 1.
In European Pat. No. 57,459, platinum/styrene complexes treated with a base are described, in which the ratio of halogen to platinum (calculated in gram-atoms of platinum and halogen) is greater than 1 but less than 4.
The platinum complexes described above have admittedly enabled advances in the state of the art, but they have at least one of the following disadvantages:
(1) they are unstable and display low catalytic activity after a relatively short storage time, on the order of one month or less;
(2) they display insufficient reactivity at a low concentration;
(3) they are particularly difficult to prepare in a simple and reproducible manner, especially as regards those described in said '459 European patent.